Capsaicin is included in fruits of Capsium annuum Linne or its variety, solanaceae, in an amount of about 0.2% by weight of the fruits. Capsium annuum is adopted in the Pharmacopeia of Japan and when a tincture or a solution of Capsaicin is put on certain area of skin, mucous membrane or a dog's ear, blood vessels of the area are expanded and the area is congested. Capsaicin, a main component of Capsium annuum, appears to have strong and stimulative effectiveness on receptors of circulatory and respiratory reflex. In experiments of internal organs removed from humans or experimental animals, a tincture of Capsium annuum or Capsaicin promotes digestion and its small amount promotes salivary and gastric secretion, however its large amount suppresses the salivary and gastric secretion. The tincture of Capsium annuum is used as a local stimulant and may be incorporated in external remedies such as plasters, solutions or ointments.
So-called capsaicin on the market, referred to hereinafter as commercial capsaicin, includes capsinoids of the following chemical structures, (1) Capsaicin (60 to 65% by weight), (2) Nordihydrocapsaicin, (3) Nonylvanillylamide, (4) Dihydrocapsaicin, (5) Decanylvanillylamide and (6) Homocapsaicin. A total amount of capsinoids in the commercial capsaicin is more than 95% by weight and a main component of the commercial capsaicin, Capsaicin, is about 60 to about 65% by weight. ##STR1##
Capsaicin have been conventionally isolated and purified by repeatedly subjecting crude capsaicin to several kinds of a large column (ODS, Phenyl, silica gel, etc.) of high performance liquid chromatography.
For example, 30 g of commercial capsaicin (60 to 65% by weight as a purity of Capsaicin) is dissolved in 300 ml of 70% methanol. The resulting solution is treated to decolor by stirring with 3 g of activated charcoal 1 hour and filtered to give a solid. The solid is dissolved in 300 ml of 70% alcohol to give a sample solution in a final concentration of 10% by weight of the solid. The sample solution is subjected to ODS column (10 cm in diameter and 50 cm in length) of high performance liquid chromatography (HPLC) to obtain fractions. Fractions including predominantly Capsaicin are collected and concentrated to give about 15 g as solid. Using the solid, 300 ml of aqueous 70% alcohol solution in a final concentration of 5% by weight of the solid is prepared and the aqueous alcohol is subjected a Phenyl column (20 cm in diameter and 100 cm in length). Fractions including predominantly Capsaicin are collected and concentrated to give a residue. The residue is dissolved in an alkaline solution, and then acetic acid is added thereto and precipitate. The obtained crystals are rinsed and dried to give 5.4 g of Capsaicin in a purity of more than 98% by weight and an yield based on commercial capsaicin is 18% by weight.
While in order to isolate Nordihydrocapsaicin having a peak near to Capsaicin's peak in HPLC and column chromatography, a method for qualitative and quantitative analysis of Capsaicin is known which comprises previously forming a silver complex and then subjecting to HPLC or column chromatography. However, the method is directed to qualitative and quantitative analysis and uses column chromatography.
And therefore, a method directed to an industrial purification without subjecting to chromatography has not been known as a method for preparing. Capsaicin in a high purity in a large scale.
According to a conventional method for purification of Capsaicin, it is difficult to remove impurities such as Nordihdrocapsaicin, Vanylamide nonylate and the like which are analogous to Capsaicin. In addition, since an amount of Capsaicin obtained by one purification procedure is severe gram order and it also depends on an amount of column-loading, usually, the column-loading amount is small, therefore, in order to obtain a large amount of Capsaicin, it is necessary to repeat the purification procedure or enlarge a column scale. Therefore, there is a limitation in the purification of Capsaicin in industrial scale and also it takes long time to obtain Capsaicin in a large quantity.